Manufacture of 1, 1, 1-trifluoroethane



Patented Aug. 16, 1949 UNITED STATE 2,478,932 MANUFACTURE or 1,1,1-rmrwono- ETHANE Charles B. Miller, St.

Bratton, Floral Park,

New York No Drawing.

Albans, and Francis E.

N. Chemical & Dye Corpo ration,

Y;, assignora to Allied a corporation of Application April 2, 1947,

. s Serial No. 138,942

This invention relates to the preparation of organic halides rich in fluorine. More specifically,.the present improvements are directed to processes for making aliphatic fluoro compounds rich in fluorine from aliphatic fluoro compounds of lower fluorine content.

Many processes are known for fluorinating organic compounds. Thus, it has been proposed to employ fluorine, hydrogen fluoride, or metallic fluorides such as mercuric fluoride and antimony trifiuoride as fluorinating agents with or without catalysts.

The principal object of our invention is to provide for manufacture of aliphatic fluoro derivatives rich in fluorine from aliphatic halofluoro derivatives of lower fluorine content by processes which do not require the use of fluorinating agents which are expensive, diificult to make and troublesome to handle and use. Another object is provision of processes for preparing fluoro derivatives of ethane containing a high fluorine content, and halofluoro derivatives of ethylene from fluohalides of ethane b means of easily controlled catalytically efiected disproportionation and dehydrohalogenation operations. More specifically, the invention aims to afford a process for the preparation of 1,1,l-trifluoroethane and 1,1 chlorofluoroethylene from 1,1,1 chlorodifluoroethane.

Other objects and advantages of the invention will appear from the following detailed description.

As applied particularly to the manufacture of 1,1,1-trifluoroethane and 1,1-chlorofluoroethylene, in accordance with the invention, we have found that these materials may be prepared by disproportionation and dehydrofluorination by heating 1,1,1-difluorochloroethane in the presence of a hereafter described aluminum fluoride catalytic material at a temperature not greater than 500' C., but sufficiently high to effect formation of 1,1,l-trifluoroethane. Preferably, reactemperature is not substantially less than In the general practice of our process, 1,1,l-difluorochloroethane, a gas at room temperature, is passed into and through a suitable reaction zone containing an aluminum fluoride catalytic material and maintained at a temperature not less than 250 C. and not greater than 500 C. with respect to formation of principal products, it is believed that the reactions effected may be summarized by the following- All 2011 ClFa 71-? CHzCF; CHFCCIF H0] I ea The reaction zone exit gas also contains some unreacted CHaCClFz.

In the more specific practice of our process, the normally gaseous 1,l,1-chlorodlfluoroethane 7 Claims. (01. 260-653) be passed through a flowmeter into a suitably jacketed graphite reactor tube which is packed with lumps or pellets of the aluminum fluoride catalytic material. The reactor tube may be mounted in an electric furnace automatically controlled to maintain the reaction zone in the tube at the desired reaction temperature.

The various reaction products may be recovered separately or in admixture from the reaction zone exit gas stream in any suitable manner. The gas discharged from the reaction zone I may be scrubbed with a caustic soda solution to remove from the gas stream HC1 and any possible traces of HF, and then dried by means of anhydrous calcium chloride. The clean dry gas stream may be then introduced into a condenser cooled to a temperature well below the boiling points of CHsCFa (-46.7" C.) CH2=CC1F (-25.5 C.), and CHsCClFz (-9.6 C.), as by means of a Dry Ice-acetone mixture. The individual reaction products may be recovered from the condensate by fractional distillation under suitable conditions, and the unreacted CHsCClFz thus obtained may be recycled to a succeeding operation.

While the exact mechanisms of the disproportionation and dehydrofluorination reactions taking place in the practice of our invention are not wholly understood, it is believed, however, that the aluminum fluoride acts essentially as a catalyst at the high temperatures stated since no appreciable amount of aluminum chloride has been found in the reaction zone exit gas. At the temperatures indicated, the aluminum fluoride catalyst brings about a disproportionation of the original halofiuoro compound, e. g. 1,1,1-ch1orodifiuoroethane, which results in a redistribution of fluorine and chlorine atoms present, accompanied by a dehydrofluorination of said 1,1,1- chlorodifluoroethane, to produce the more highly fluorinated 1,1,l-trifluoroethane and the unsaturated LI-chIorofluoroethylene. Operations show that the composition of the aluminum fluoride does not change and hence it appearsthat the aluminum fluoride does not act as a fluorinating agent in the usual sense and provides substantially no available fluorine during the course of the reaction.

The aluminum fluoride catalytic material which we employ in the reaction may be (a) substantially pure aluminum fluoride, or (b) a complex basic aluminum fluoride, or (0) mixtures of both. In any case, the catalytic material should contain not less than 55 parts by weight of fluorine per 100 parts by weight of such material,- these values referring to the catalytically efiective material per se without regard to any non-deleterious or inert solid substances which are incidentally" present as impurities or diluents. It is preferred to employ aluminumfluorlde which is as pure as may commercially feasible.

C. Good necessary to provide adequate maintained at 325 presence of an aluminum fluoride the sought-for highly fluorinated reaction products, e. g. 1,1,1-trifluoroethane, increase at higher tempera In order to avoid decomposition, loss of other valuable reaction products, e. g. 1,1-chlorofluoroethylene, and decreased yields of the chief product, 1,1,1-trifluoroethane, reaction zone temperatures should not exceed about 500 C. and preferably not more than 400 commercial yields are obtained when reaction zone temperatures are held substantially within the range of 250-400 0., and best over-all results may be secured when operating at temperatures of the order of 300-400 C.

Any suitable chamber or reactor tube constructed of inert material ma be employed for carrying out the reaction, provided the reaction zone afl'orded is of Bilflicient length and crosssectional area to accommodate the required amount of aluminum fluoride catalytic material gas contact area, and at the same time afford sufllcient free space for passage of the gas mixture at an economical rate of flow. In practice of the invention, rate of feed of incoming gas into the reaction zone may be any suitable value, depending upon the conditions at hand, such as to afford reaction time sufllcient to facilitate good commercial recoveries of products.

The 1,1,1-trifluoroethane and 1,1-chlorofluoroethylene prepared by the process of the invention are utilizable particularly as a refrigerant and monomer respectively, and as intermediates in thechemical industries.

The following example serves to illustrate in some detail the practice of our invention:

A reactor tube was packed with aluminum fluoride pellets prepared from reagent-grade material which was substantially pure aluminum fluoride. The reactor tube was constructed of glass, and had an inside diameter of 25 mm. The tube contained a catalyst bed 15 inches long, thus providing an aluminum fluoride volume of 190 cc. The tube was heated in an electric furnace and g C. by a control potentiometer.

439 parts (by weight) of. gaseous 1,1,1-chlorodifluoroethane were passed through the reactor tube at a rate of 100 parts per hour. The exit gas of the reaction zone was then passed into a condenser cooled to about -78 C. by means of a Dry Ice-acetone mixture, and 340 puts of condensate were thus obtained. The condensate so collected was fractionated to recover the individual components, indicating the following amounts of 91% and a carbon recovery of 90%. The major product formed was CHsCF; which contained weight of said catalytic of products:

CHaCFa- 122 CH2=CC1F 106 CHaCClF: 116 These materials represent a fluorine recovery 50% of the fluorine charged while CHz=CClF represented 15% of the fluorine charged.

We claim: v 1. The process which comprises heating 1,1,1- difluorochloroethane at a temperaturenot less than 250 C. and not greater than 500 C. in the catalytic maof, said catalytic 4 terial of the group consisting of aluminum fluoride, a complex basic aluminum fluoride and mixtures thereof, said catalytic material containing not less than 55 parts by weight of fluorine per parts by weight of said catalytic material.

2. The process which comprises heating 1,1,1- difluorochloroethane at a temperature not less than 250 C. and not greater than 500 C. in the presence of an aluminum fluoride catalytic material of the group consisting of aluminum fluoride, a complex basic aluminum fluoride and mixtures thereof, said catalytic material containing not less than 55 parts by weight of fluorine per 100 parts by weight of said catalytic material, and recovering 1,1,1-trifluoroethane from the resulting reaction mixture.

3. The process which comprises heating 1,1,1- difluorochloroethane at a, temperature not less than 250 C. and not greater than 500 C. in the presence of substantially pure aluminum fluoride, and recovering 1,l,1,-trifluoroethane from the resulting reaction mixture.

4. The process of producing 1,l,1-trifluoroethane and 1,1-ch1orofluoroethylene by disproportionation and dehydrohalogenation, comprising contacting 1,1,1-difluorochloroethane with an aluminum fluoride catalytic material of the group consisting Of aluminum fluoride, a complex basic aluminum fluoride and mixtures therematerial containing not less than 55 parts by weight of fluorine per 100 parts by weight ofsaid catalytic material, at a tem perature not less than 250 C. and not greater than 500 C.

5. The process which comprises heating 1,1,1- difiuorochloroethane at a temperature in the range of 250 to 400 C. in the presence of an aluminum fluoride catalytic material of the group consisting of aluminum fluoride, a complex basic aluminum fluoride and mixtures thereof, said catalytic material containing not less than 55 parts by weight of fluorine per 100 parts by material.

6. The process of producing 1,1,1-trifluoroethane and 1,1-chlorofluoroethylene by disproportionation and dehydrohalogenation, comprising contacting 1,1,1-difluorochloroethane with an aluminum fluoride catalytic material of the group um fluoride, a complex basic and mixtures thereof, containing not less than 55 parts by weight of fluorine per 100 parts by weight of said catalytic material, at a temperature in the range of 300 to 400 C.

7. The process of tionation and dehydrohalogenation, comprising passing 1,1,1-difluorochloroethane into a reaction zone containin oride andmaintained at a temperature in the range of 300 to 400 C., and recovering 1,1,1- trifluoroethane and 1,1-chlorofluoroethylene from the reaction zone exit gas.

CHARLES B. MILLER.

FRANCIS H. BRATTON.

- REFERENCES CITED The following references are of record in the flle of this, patent:

V UNITED v STATES PATENTS Number Name Date 1,994,035 Croco Mar. 12, 1935 2,426,637 Murray Sept. 2, 1947 2,426,638 Murray Sept. 2, 1947 substantially pure aluminum flu-- 

